Electrophotographic photosensitive material

ABSTRACT

AN ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MATERIAL WHICH COMPRISES POLY-9-VINYLCARBAZOLE OR DERIVATIVE THEREOF AND A DIALKYLAMINOSTYRYL DYE.

March 12, 1974 E||H| KQNDQ ETAL ELECTROPHOTOGHAPHIC PHOTOSENS I'I'IVEMATER IAL Filed Nov. 11, 1971 -o'.3-o'.2-o'.| (5 oil 0Y2 0'3 0'.4 0'5o'.e 0'7 (is OOF SUBSTITUENT x (HAMMETT'S SUBSTITUENT CONSTANT) FIG. 2

460 560 660 766m FIG. 3

F l G. 4

660 YcEm United States Patent U.S. Cl. 945-16 7 Claims ABSTRACT OF THEDISCLOSURE An electrophotographic photosensitive material whichcomprises poly-9-vinylcarbaz0le or derivative thereof and adialkylaminostyryl dye.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to highly sensitive electrophotographic photosensitive materialsmainly composed of organic photoconductive compounds.

Description of the prior art Among organic photoconductive compoundsused as photoelectric photosensitive materials, some have a considerablyhigh sensitivity, but it is very rare that they are used in practice atpresent. Organic photoconductive compounds have various more excellentcharacteristics than inorganic ocmpounds and promise variousapplications in the field of electrophotography. For example, it ispossible only by use of organic photoconductive compounds to providetransparent photosensitive films, flexible photosensitive films orphotosensitive films which are light in weight and easy to handle.Furthermore, organic photoconductive compounds can give a photosensitivemember having film shapeability, surface smoothness and selectivity ofcharging polarity in an electrophotographic reproduction process. Theseexcellent properties are not expected in the case of an inorganicphotoconductive compound. However, organic photoconductive compoundshave not been practically used for a photosensitive member ofelectrophotography in spite of their many excellent properties sincetheir photosensitivity is low.

In the early years the investigation of organic photoconductivecompounds was mainly directed to various macromolecule type aromatic orheterocyclic compounds, all of which have a complicated structure, andsome highly sensitive organic photoconductive compounds were discovered.However, the recent trend is toward the optical or chemicalsensitization in order to attain higher sensitivity because even a knownorganic photoconductive compound having the highest sensitivity cannotbe used without optical or chemical sensitization as its sensitivity istoo low to be used in practice. It is, therefore, essential to utilizethe most effective optical or chemical sensitization when organicphotoconductive compounds are used in practice, and the commercialvalues of organic photoconductive compounds are dependent upon how theyare optically or chemically sensitized to provide photosensitivematerials having a sufliciently high sensitivity.

The most general sensitization method is to add sensitizing dyes orLewis acid, and these two methods can be applied to all of organicphotoconductive compounds without exception. When the sensitizing dye isadded, their specific spectral absorptions are added to those of theorganic photoconductive compounds. When Lewis acid is 3,796,569 PatentedMar. 12,, 1974 Ice added, the complex of doner and acceptor is formedbetween the organic photoconductive compound and the Lewis acid so thatthe new spectral sensitivity bands (C-T band) appear.

However, the sensitivity attained by the above described methods isstill too low to be used in the electrophotographic process.

There have been known various organic photoconductive compounds, andthey are, for example,

(A) Vinylcarbazoles: poly-9-vinylcarbazole, 9-vinylcarbazole copolymer,3-nitro-9-vinylcarbazole copolymer, nitrated poly-9-vinylcarbazole,poly-9-vinyl-3-aminocarbazole, 3 N methylamino-9-vinylcarbazolecopolymer, halogen-substituted poly-vinylcarbazole,poly-3,6-dibromo-9-vinylcarbazole, 3,6 -dibromo-9-vinylcarbazolecopolymer, brominated poly-9-vinylcarbazole, 3-iodo-9- vinylcarbazolecopolymer, poly-3,6-diiodo-9-vinylcarbazole,poly-3-benzylideneamino-9-vinylcarbazole, poly-9- propenylcarbazole,graft copolymer of 9-vinylcarbaz0le and ethylacrylate (90:10 inpolymerization mol ratio), vinylanthracene-9-vinylcarbazole copolymer,homopolymer or copolymer of 2-(or 3-) vinyl-9-alkylcarbazole (wherealkyl group is a primary alkyl group such as methyl, ethyl, propyl,etc.) and the like.

(B) Aromatic amino derivatives: aminopolyphenyl, arylideneazines,N,N'-dialkyl-N,N'-dibenzylphenylenediamine,N,N,N',N'-tetrabenzyl-p-phenyldiamine, N,N'-diphenyl-p-phenylenediamine,N,N'-dinaphthyl p phenylenediamine, 4,4 -bis-dimethylaminobenzophenone,and the like. i

(C) Diphenylmethane and triphenyl methane series: diphenylmethane dyeleuco base, triphenylmethane dye leuco base, and the like.

(D) Heterocyclic compounds: oxadiazole, 9-ethylcarbazole,9-n-hexylcarbazole, S-aminothiazole, 1,2,4-triazole, imidazoline,oxazole, imidazole, pyrazoline, imidalizine, polyphenylenethiazole,1,6-methoxyphenazine, a,wbis-(9-carbazole)-alkane derivative,pyrazolinopyrazoline derivatives, and the like.

(E) Those having condensed rings: benzthiazole, benzimidazole,2-(4'-diaminophenyl) benzoxazole, 2-(4'-dimethylaminophenyl)benzoxazole, aminoacridine, quinoxaline, diphenylenehydrazones,pyrrocoline derivatives, 9,10-dihydroanthracene derivatives, and thelike.

(F) Compounds having a double bond: acylhydrazone, ethylene derivatives,-l,l,6,6 tetraphenylhex'atniene, 1,1,5- triphenyl-pent-1-ene-4-ine-3-ol;and the like.

(G) Condensation compounds: condensation ,compounds of aldehyde andaromatic amines, reaction products of secondary aromatic amines andaromatic halogenides, polypyromethanoimide, poly P phenylene-l,3,4-oxadiazole, and so on.

(H) Vinylpolymers (except polyvinylcarbazoles):u-alkylacrylamidepolymers; polyvinylacridine, poly-[1,5-diphenyl-3-(4-vinylphenyl)-2-pyrazoline] poly (LS-diphenylpyrazoline);polyacenaphthylene; nucleus-substitutedpolyacenaphthylene;polyvinylanthracene; p'oly-2-vinyldibenzothiophene, and so on.

(I) Organic photoconductive oligomers:

where l, m and n are 0 or I and m; n.

Examples of oligomers are:

as 5 ring compound p-bis-(2-phenyl-4-thiazolyl)benzene, as 7 ringcompound 2,4-bis- [4- (2-phenyl-4-thiazolyl) -phenyl] thiazole and as 9ring compound 1,4 bis [4 {4 (2 phenyl 4 thiazole)-phenyl}-thiazolyl1benzene.

Some of the above listed organic photoconductive compounds may besensitized by the prior art sensitization methods to have a sulficientlyhigh sensitivity, but the others are not suificiently sensitized. It istherefore desired to find out a suitable sensitization method dependingupon the kinds of organic photoconductive compounds whereby they aresatisfactorily utilized as the electrophotographic photosensitivematerials.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided an electrophotographic photosensitive material whichcomprises an organic photoconductive material selected from the groupconsisting of poly-9-vinylcarbazole and derivatives thereof and at leastone of dialkylaminostyryl dyes having the formula:

wherein R is hydrogen or loweralkyl (including loweralkenyl) and R is,similar or dissimilar, selected from the group consisting of hydrogenand loweralkyl (including loweralkenyl); R and R are, similar ordissimilar, selected from the group consisting of hydrogen andsubstituents having Hammetts substituent constant anot lower than 0.2,but R and R should not be simultaneously hydrogen; R is an alkyl having6 to 12 carbon atoms; R; and R are, similar or dissimilar, loweralkyl; Xis an anion; and n is 1 or 2.

An object of this invention is to provide an excellent method ofsensitizing organic photoconductive compounds and further to provide anorganic photosensitive material for electrophotography of highphotosensitivity which can be practically used.

Another object of this invention is to provide a photosensitive filmwhich is highly sensitive, transparent, flexible, light and of easyhandling.

A further object of this invention is to provide a photosensitivematerial which is sensitive to all visible lights.

Another object of this invention is to provide a photosensitive materialfor multicolor electrophotography capable of color separationphotographing by using a color separation filter.

A further object of this invention is to provide a stable organicphotoconductor photosensitive material which potential characteristicssuch as surface potential, dark decay and the like are not disturbed bythe addition of a sensitizing dye.

Another object of this invention is to provide an organic photoconductorphotosensitive plate in which the compatibility of an organicphotoconductor and a sensitizing dye is so excellent that there is not afluctuation of quality upon production.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a graph showing a relationbetween log E where E is photosensitivity as defined in Example 1 belowand a value; and

FIG. 2, FIG. 3 and FIG. 4 show spectral sensitivity of somedialkylaminostyryl dyes used in this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Dialkylaminostyryl dyes used inthe present invention may be prepared by conventional methods, forexample, as shown below.

(1) A compound of the formula A I/ LOH, R Z 2 R3 X is condensed with acompound of the formula /R4 /R4 OHC N or 0HCCH=CH- N by heating them inan alcohol in the presence of piperidine.

In the above formulas, R R R R R A and X are as defined above.

(2) The reactants are heated in acetic anhydride to condensate them.

The present inventors have found that the above mentioneddialkylaminostyryl dye is particularly effective forpoly-9-vinylcarbazole or derivatives thereof as a sensitizer. The rangesensitized by the dialkylaminostyryl, dye according to this inventionwidely covers Whole visible wave length, and particularly shows highresponse to green light. In examples, there are given comparisonsbetween the sensitization according to this invention and that caused bya compound having a chemical structure similar to the dialkylaminostyryldye within the scope of this invention. The difference of thesensitizing effect therebetween is remarkable and it has been found thatthere is a certain rule with respect to the substituent effect.

The mechanism of dye sensitization to organic photoconductive compoundsis not yet generally known, but the present inventors have recognizedthat sensitization elfect of dye is, in general, closely related to thechemical structure of the dye. The present inventors have found that thelarger the electron attractivity of substituent on the benzenoid moietyof the nucleus containing A and N in the above formula such asimidazole, oxazole, thiazole, selenazole, pyrrole and pyridine rings,the higher the sensitization effect.

When at least one of R and R is a halogen such as Cl, Br and I, nitro orCOOR where R is loweralkyl, the dialkylaminostyryl dye shows far bettersensitization effect than that having unsubstituted benzenoid moiety ofthe nucleus containing A and N. R and R are preferably lower alkyl ofnot higher than C The sensitization effect of the substituent isapproximately proportional to the Hammetts substituent constant (0'). Asillustrated in FIG. 1 where the ordinate is log E where E isphotosensitivity and abscissa is I-Iammetts 0' value, the relation isshown by a straight line.

Hammetts substituent constant is described in L. P. Hammett: PhysicalOrganic Chemistry, page 78 (published by McGraw-Hill Book Co., N.Y.,1940) and D. H. McDaniel, H. C. Brown: J. Org. Chem. 23, 420 (1958).

0' values of representative substituents are shown in Table 1 below.

The Hammett's value used in the present invention is higher than 0.2,preferred with from 0.2 to 0.8. A particularly preferable value rangesfrom 0.35 to 0.8.

Carbon number of alkyl of R in the general formula of dialkylaminostyryldye used in this invention remarkably affects the sensitization abilityof the dialkylaminostyryl dye. This will be shown later.

In case of silver halide photosensitive material, there are measuredspectral reflectivity of dialkylaminostyryl dye absorbed to the surfaceof silver halide, and monomer absorption, dimer absorption andaggregation absorption are known.

In the present invention, a relation among carbon number of R in thegeneral formula of the dialkylaminostyryl dye, spectral reflectivity ofdialkylaminostyryl dye in poly-9-vinylcarbazole and sensitizationefficiency is investigated and the following matter is observed. Whencarbon number of R is 2-5, there are observed aggregation absorption,dimer absorption and trimer absorption while at carbon number of R being6 or more the aggregation absorption is hardly observed, but onlymonomer absorption and dimer absorption are observed.

Further, it is observed that the sensitization efiiciency is inverselyproportional to the amount of aggregation absorption and carbon numberof 6 or more gives particularly high sensitivity.

A dialkylaminostyryl dye having R of more than 12 carbon atoms cannot beeasily synthesized and is obtained at low yield. Therefore, such adialkylaminostyryl dye is not advantageous from a commercial point ofview.

Representative organic photoconductive compounds used in this inventionare:

poly-9-vinyl carbazole (cf. US. Pat. 3,037,861);

poly-3-vinyl-9 alky1 carbazole (cf. ibid.);

chlorinated po1y-9-vinyl carbazole (chlorine content, 2-43% by weight),for example, poly-3-chloro-9- vinylcarbazole,poly-3,6-diohloro-9-vinylcarbazole (Belgian Pat. 753,619);

brominated poly-9-vinylcarblazole (bromine content,

17-46% by weight), for example, poly-3,6-dibromo- 9-vinylcarbazole etc.(Japanese Patent Publication Nos. 19,75 1/ 1969 and 25,230/ 1967chlorinated brominated poly-9-vinylcarbazole;

chlorinated iodinate poly-9-viny1carbazole;

cyanated poly-9-vinylcarbazole;

thiocyanated poly-9-vinylcarbazole (the above two compounds aredescribed in Japanese Patent Application Nos. 15,055 1970 and98,528/1970) poly-3-methyl- 9-vinylcarbazole;

and chlorinated poly-3-methyl-9-vinylcarbazole, for examplepoly-3-methyl-6-chloro-9-vinylcarbazole (Japanese Patent Application No.66,005/1970).

It is known that the above mentioned polyvinyl carbazole and derivativesthereof have specific stereostructures. This specific configurationcauses overlap of 1r-electron of carbazole ring and thereby aparticularly excellent photoconductivity is obtained.

However, poly-9-viny1carbazole and derivatives thereof are sensitiveonly to ultraviolet region, but not to visible light. Therefore,photosensitivity of non-sensitized photosensitive plate ofpoly-9-vinylcarbazole series for tungsten lamp is about 10 lux.sec. andis almost the same as that of non-sensitized photosensitive platecomposed of a photoconductor of low molecular weight and a binder resin.

However when the poly-9-vinylcarbazoles are sensitized by cyanine dyeaccording to this invention, the photosensitive plate made of them showsphotosensitivity of 2X 10 to 10 lux.sec. while the photosensitive platecomposed of a photoconductor of low molecular weight and a binder resinsensitized according to this invention shows a photosensitivity of 5X10to 5x10 lux.sec. Therefore, the photosensitivity obtained by thisinvention is about ten times that of the conventional one.

Some preparation methods of poly-9-vinylcarbazole derivatives used inthis invention are shown below.

Chlorinated poly-9-vinylcarbazole, brominated poly-9- vinylcarbazole,and chlorinated brominated poly-9-vinylcarbazole may be prepared byreacting poly-9-vinylcarbazole with an appropriate chlorinating agentand/or brominating agent. 9-(p-chloroethyl) carbazole or 9-(3-hydroxyethyl) carbazole is chlorinated or brominated followed bydehydrochlorination and dehydrating treatment to give chlorinated orbrominated vinylcarbazole. The resulting vinylcarbazole ishomopolymerized or copolymerized to produce the halogenatedpoly-9-vinylcarbazoles. Chlorinated poly-9-vinylcarbazole is obtained byreacting a chlorination agent such as chlorine or sulfuryl chloride withpoly-9-viny1carbazole. Some examples of syntheses will be describedbelow.

PREPARATION EXAMPLE 1 added to Reaction 20% solutempera/- Yield,Experiment No. tion, ml. ture, 0 grams Chlorinated poly-9-carbazole ispurified by reprecipitation from monochlorobenzene-methanol.

Analysis Experiment No. 01 N The resulting chlorinatedpoly-9-vinylcarbazole contains chlorine substantially equivalent to thatin sulfuryl chloride used. When it is desired to obtain chlorinatedpoly-9- vinylcarbazole with a high chlorine content (especially higherthan 30%), monochlorobenzene solvent is used.

PREPARATION EXAMPLE 2 This is an example of obtainingchlorinated-brominated 9-vinylcarbazole.

4.0 grams of 3-chlorocarbazole is suspended in 20 ml. of carbonbisulfide and while the mixture is refluxed, the solution of 3.2 gramsof bromine in 220 ml. of carbon bisulfide is dropped for one hour. Aftercooling at room temperature, crystals are obtained by filtration andrecrystallized from glacial acetic acid. 4.5 grams of 3-chloro-6-bromocarbazole are obtained with a yield of about 80%, melting point198 C. (l97l98 C. in literatures). 3-chloro-6-bromocarbazole may beobtained by brominating carbazole into 3-bromocarbazole (M.P.=201 C.)and then chlorinating it. 4.0 grams of 3-chloro-6-bromocarbazole, 0.07gram of caustic potash powder and 5 ml. of methylcyclohexane are reactedin an autoclave 100 ml. in volume at C. for six hours while intro ducingacetylene (the initial gage pressure=about 25 atms.)..After cooling, thereaction product is poured into water and the precipitants are obtainedby filtration and recrystallized from n-hexane solution. 3.3 grams of3-chloro-6-bromo-9-vinylcarbazole is obtained with a yield of 76% andmelting point 135 C.

Analysis.-Found (percent): C, 54.0; H, 2.86; N, 4.50; Cl, 11.0; Br,25.0. Calcd. (percent): C, 54.8; H, 2.94; N, 4.57; Cl, 11.6; Br, 26.1.

3-chloro-6-bromo-9-vinylcarbazole may be obtained by brominating9-fl-chloroethylcarbazole or 9-ethylolcarbazole and then chlorinatingand treating with alcoholic caustic potash. Next 1.0 gram of3-chloro-6-bromo-9- vinylcarbazole in 3.0 ml. of acetonitrile in a hardglass polymerization tube is exposed to a high-pressure mercury vaporlamp, and the exposing is continued for thirty minutes after gelation.Then methanol is added and the resulting precipitate is separated byfiltration, dissolved into benzene and then precipitated again by addingmethanol. These steps are repeated twice. 0.6 gram of white polymer isobtained with a yield of about 60%, and the intrinsic viscosity inbenzene is [1;]=0.45.

Thiocyanated poly-9-vinylcarbazole used as an organic photoconductivecompound in this invention may be prepared by the reaction ofpoly-9-vinylcarbazole with a thiacyanogen as described below. Thethiocyanated poly- 9-vinylcarbazole may be further obtained by othermethods such as reaction of poly-9-vinylcarbazole with sodiumthiocyanate and bromine.

PREPARATION EXAMPLE 3 Poly-9-vinylcarbazole (5.0 g.) is dissolved in 160ml. of chlorobenzene, and then a chlorobenzene solution of athiacyanogen obtained from lead thiocyanate and equivalent amount ofbromine (cf. Organic Reactions, vol. 3, p. 255) is gradually addedthereto with agitation at a temperature lower than C. and the reactionis carried out for 3 hours. The reaction temperature is preferably lowas far as the reactivity of the reagent is not deteriorated since a sidereaction occurs at high temperature to form gel. Then, the reactionmixture is poured into a large amount of methanol to precipitate thepolymer, washed with methanol, and dried under vacuum. The polymer thusobtained is further purified by the reprecipitation fromchlorobenzene-methanol. According to the above-mentioned method, thefollowing polymers are prepared.

Amount Reaction of thiatempercyanogen ature Yield (grams) C.) (grams)Analysis and solubility of the above-mentioned polymers are shown below.

Nora: O=soluble; A=hardly soluble; X=insoluble.

In infrared spectrophotometry, the absorption wavelengths are 2145 cm.(--CEN), 860 cm.- and 790 cm.- (benzene nucleus substituted at 1, 3 and4 positions), so that it is considered that -SCN groups are substitutedat 3 or at 3 and 6 positions of a carbazole ring.

8 PREPARATION EXAMPLE 4 Cyanated poly-9-vinylcarbazole may be obtainedin the following manner:

Five grams of poly-9-vinylcarbazole is dissolved into 50 cc. of pyridineand added with 6.6 grams of iodine and is agitated at C. for 3 hours.After being cooled, the mixture is poured into a large quantity ofmethanol to precipitate the polymer, which is filtered, dried,precipitated again and purified in pyridine-methanol solution. Thepolymer thus obtained is iodinated-poly-9-vinylcarbazole with an iodinecontent of 20.49%.

Two grams of iodinated-poly-9-vinylcarbazole is dissolved into 50 cc. ofN-methyl-Z-pyrrolidone and is added with 0.5 gram of cuprous cyanide.The mixture is agitated at C. for 6 hours. After cooling, the reactionmixture is poured into a large amount of a mixture of methanol andaqueous ammonia (4:1, volume ratio) to precipitate the polymer. Thepolymer thus precipitated is filtered, dried, reprecipitated withtetrahydrofuranmethanol, and purified. The resulting polymer is whiteand soluble in organic solvents such as tetrahydrofuran, pyridine,chlorobenzene, and so on. In infrared spectrophotography, the absorptiondue to the presence of cyano group is observed at 2210 cm." while theabsorption due to the substitution at 3 position of a carbazole ring wasobserved at 890 cm? and 805 cmr No iodine is detected and a nitrogencontent 9.65% well corresponds to the calculated value. Therefore it isseen that the above reaction is quantitative and that a cyano groupoccupies the 3 position of a carbazole ring. Thus the polymer obtainedis cyanated poly-9-vinylcarbaz0le.

Further, examples of preparing poly-'3-methyl-9-vinylcarbazole andchlorinated poly-3-methyl-9-vinylcarbazole are shown below.

as described in F. Ullmann: Liebigs Annalen der Chemie, 332 82-104(1904).

of sodium carbonate containing 10% of n.propanol NO: I Dissolved insodium hydroxide lBoiled in a 2.5 M aqueous solution and reduced withaluminum powder (M.P. 182 C o) In a diluted sulfuric acid; Sodiumnitrite is added.

HzCQ-NHQ-C OOH (M.P. 267 C lDry distillation on quick lime (M.P. 200 C.)

The resulting 3-methylcarbazole is heated in acetone together with 1.5mole of powdered potassium hydroxide and 1.1 mole ofp-chloroethyl-p-toluene sulfonate for 5 hours, then poured into water,neutralized to precipitate oily matter. The oily matter thusprecipitated crystallizes upon standing. The resulting crystals arerecrystallized from methanol to obtain9-fl-chloroethyl-3-meth*ylcarbazole, which is heated with an alcoholicpotassium hydroxide to produce 3-methyl-9 vinylcarbazole. The resulting3-methyl-9-vinylcarbazole is distilled and recrystallized. The3-methyl-9-vinylcarbazole thus purified (4.0 g.) is placed in apolymerization tube of Pyrex, evacuated with nitrogen, and irradiated bya high pressure mercury lamp at 80 C. to effect the polymerization.After about 6 hours, the polymerization product is dissolved in benzeneand then precipitated with methanol to obtain white polymer,poly-3-methy1-9-vinylcarbazole, about 2.8 g. (conversion, 70%, intrinsicviscosity in benzene [1;]=0.1.

PREPARATION EXAMPLE 6 Poly-3-methyl-9-vinylcarbazole (4.0 g.) obtainedin Preparation Example 5 is dissolved in 160 cc. of dry chlorobenzenewith agitation at C., and 26 cc. of a 20% solution of sulfuryl chloridein methylene chloride is dropwise added thereto, and the reaction iscarried out at 30 C. for 4 hours. The reaction mixture is then pouredinto a large amount of methanol to precipitate the polymer, washed 'withmethanol and dried under vacuum to give a chlorinated poly-3-methy1-9vinylcarbazole containing about 14% by weight of chlorine.

Chlorinated polyvinylcarbazole used in the present invention as anorganic photoconductive compound is described in Japanese patentapplication Nos. 56,806/ 19 69 9,837/ 1970 and 53,816/ 1970.

Representative dialkylaminostyryl dyes used in the present inventionare:

.2-p-dimethylaminobenzylidenemethyl-6-dichlorobenzthiazole-n-hexyliodide, Z-p-dimethylaminobenzylidenemethyl-S-nitrobenzthiazolen-octylperchlorate,2-p-dimethylaminobenzylidenemethyl-S-carbethoxybenzthiazole-n-nonyliodide, 2-p dimethylaminobenzylidenemethyl-6-bromobenzselenazole-n-hexylperchlorate,2-p-dimethylaminobenzylidenemethyl-6-chlorobenzselenazole-n-octyliodide, 2-pdimethylaminobenzylidenemethyl-3,3-dimethyl-5-nitroindole-n-octyl perchlorate,Z-p-dimethylaminobenzylidenemethyl-3,3-dimethyl-- iodoindole-n-octylperchlorate, 2-p-dimethylaminobenzylidenemethyl-3,3-dimethyl-5-bromoindole-n-octyl perchlorate,

2-p-dimethylaminobenzylidenemethyl-S-bromoindole-nhexyl perchlorate,2-p-dimethylaminobenzylidenemethyl-3,3-dimethyl-5- chloroindole-n-octylperchlorate, Z-p-dimethylaminobenzylidenemethyl-6-nitroquinoline-noctylperchlorate, Z-p-di-n-butylaminobenzylidenemethyl-6-iodoquinoline-nhexyl iodide, 4-p-dimethylaminobenzylidenemethyl-6-nitroquinoline-nhexyliodide, 4-p-dimethylaminobenzylidenemethyl-6bromoquinolinen-octyliodide, 2-p-dimethylaminocinnamylidenemethyl-6-iodoquinolinen-octylperchlorate,2-p-dimethylaminocinnamylidenemethyl-6-bromoquinoline-n-hexyl iodide,2-p-dimethylaminocinnamylidenemethyl-3,3-dimethyl-5- nitroindole-n-hexylperchlorate, and 2-p-dimethylaminocinnamylidenemethyl-3,3-dimethyl-5-chloroindole-n-octyl perchlorate.

The anion function of the above compounds may be exchanged with anionsof other acids to form various compounds.

From an economical point of view, dialkylaminostyryl dyes of the aboveformula where R and R are selected from chloro, bromo, iodo and nitroand are preferable since synthesis of them is easier than that of otherdialkylaminostyryl dyes.

The carbon number of alkyl group of R and R does not largely affect thesensitization ability of the dialkylaminostyryl dye, but solubilitythereof in solvents. In general, the more the carbon number, the higherthe solubility in solvents.

The electrophotographic photosensitive material according to the presentinvention may be made into a photosensitive member by dissolving ordispersing the organic photoconductive material, the dialkylaminostyryldye and if desired, binder, plasticizer or other additives in a solvent,coating on a conductive support and drying, or melting theabove-mentioned ingredients and coating on a conductive support, orproducing a self-supporting photosensitive film from a solutioncontaining the above-mentioned ingredients by evaporating the solvent orby melting and extruding the above-mentioned ingredients.

The above-mentioned photosensitive material may contain, in addition todialkylaminostyryl dye, conventional sensitizing dyes as described in,for example, Yuki Gosei Kagaku Kyokai-shi, 24, 1010-1027 (1966), such ascrystal violet, malachite green, methylene blue, and the like, andfurther may contain chemical sensitizers, for example, Lewis acid suchas picric acid, S-nitroacenaphthene, 2,4,7-trinitrofluoroenone, maleicanhydride, chloroacetic acid, and anthraquinone.

The above sensitizing dyes are added to the organic photoconductivematerial preferably in an amount of 0.01-2% by weight based on theorganic photoconductive material. They may be added to a solution of theorganic photoconductive material in a form of methanol, chloroform ordimethylformamide solution.

The following examples are given for illustrating the present invention,but should not be construed as restricting the present invention.

EXAMPLE 1 One gram of chlorinated poly-9-vinylcarbazole (chlorinecontent, 27.5%) was dissolved in 15 ml. of monochlorobenzene. A solutionof dialkylaminostyryl dye in chloroform was added to the solutionobtained above in an amount of 0.1 mole percent. The resulting solutionwas coated on a high grade paper processed with polyvinylalcohol byusing a wire-bar and dried to produce a photosensitive paper having aphotosensitive layer of about 6 microns thick.

The photosensitive paper thus obtained was seasoned and then chargedwith an electrostatic paper analyzer (supplied by Kawaguchi Denki) andexposed to measure the exposure amount necessary for decreasing theinitial potential to $6 of the initial potential. The result is shown inTable 2 below as photosensitivity.

The above-mentioned photosensitive paper was charged and the spectralsensitivity was measured by a spectral camera. The peak is listed inTable 2 below as photosensitivity peak.

Dialkylaminostyryl dyes used in the present example are represented bythe following formula:

n-CaHu C104 TABLE 2 Photo- Photosensi- Dye sensitivity No. X Y Z Man.tivlty 3 peak 3 1- S H H 526 160 570 H 541 120 580 H 535 120 580 H 540101 590 H 545 90 600 C1 552 95 600 H 567 70 620 H 548 130 580 H 555 95595 H 556 95 595 H 563 90 600 H 532 75 620 H 528 120 590 H 535 90 605 H538 90 605 H 543 80 610 H 569 55 635 1 Spectral absorption maximum (mp)in a methanol solution.

2 Exposure amount (lux.sec.) necessary for decreasing an initialpotential to 1/10.

8 Maximum (mg) of spectral sensitivity.

In Table 2 above, dye numbers 1, 8 and 13 are not within the scope ofthe present invention and are given for comparison withdialkylaminostyryl dyes of the present invention. The result shown inTable 2 indicates that when the substituents Y and Z are those havinghigh electron attractivity, the sensitization effect is large.

Spectral sensitivity curves for dye numbers 2, 7, and 12 are shown inFIGS. 2, 3 and 4, respectively.

Reference numbers 1-7 in FIG. 1 correspond to dye numbers l-7 in Table2, respectively.

EMMPLE 2 Two grams of poly-9-vinylcarbazole (Luvican M-l70, trade name,supplied by Badische Anilin und Soda- Fabrik) was dissolved in 15 ml. oftetrahydrofuran. mg. of 2-p-dimethylaminocinnamylidenemethyl 6nitrobenzthiazole-n-octyl perchlorate dissolved in 2 ml. ofdimethylformamide was added to the solution obtained above, and then 0.5g. of chlorinated parafiin (chlorine content, 40%) was added thereto.The resulting solution was coated on an art paper to form aphotosensitive layer of 6p. (when dried) thick and dried at 100 C. for 5minutes. The resulting photosensitive paper was charged, exposed by aphotographic enlarger and developed. The optimum exposure was 75lux.sec. and the spectral photosensitivity peak was 680 mbromobenzoxazole-n-octyl perchlorate 150 (c) 2 pdimethylaminobenzylidenemethyl 6 bromobenzselenazole-n-hexyl perchlorate100 (d) 2 p dimethylaminobenzylidenemethyl 5 nitroindole-n-octylperchlorate (e) 2 p dimethylaminocinnamylidenemethyl 6bromobenzthiazole-n-dodecyl perchlorate EXAMPLE 4 Poly-9-vinylcarbazoleg 2 Carbon tetrabromide g 0.1 9-vinylcarbazole g 0.1 Benzene ml 40 Theabove ingredients are uniformly mixed and exposed to a 450 w. mercurylamp at a distance of 10 cm. for 5 minutes. After completion of thereaction, 10 mg. of 4-p-dimethylaminobenzylidenemethyl 6nitroquinoline-n-octyl perchlorate in 5 ml. of chloroform was added tothe reaction solution. The resulting solution was coated on a high gradepaper having a polyvinylalcohol layer to form a coating of 51.0 thick(when dried) followed by drying.

The resulting photosensitive paper Was subjected to anelectrophotographic process in a way similar to Example 2 and goodimages were obtained. The optimum exposure amount was lux.sec. whileoptimum exposure amount for a photosensitive paper containing nosensitizing dye was 150 lux.sec.

EXAMPLE 5 Poly-9-vinylcarbazo1e [as shown in Table 3, (l) to g 0.2%solution ofZ-p-dimethylaminobenzylidenemethyl-6-nitrobenzthiazole-n-hexylperchlorate in chloroform ml 5 Tetrahydrofuran ml 30 TABLE 3Poly-9-vinylcarbazole type Sensitivity organic photoconductor:(lux.sec.)

(1) Chlorinated poly-9-vinylcarbazole (chlorine content, 24.8%) (2)Poly-3-bromo-6-chloro-9-vinylcarbazole 95 (3) Chlorinated brominatedpoly-9-vinylcarbazole (chlorine content, 13.2%; bromine content, 15.0%)(4) Cyanogenated poly-9-vinylcarbazole (nitrogen content, 9.65%) 75 (5)Thiocyanated poly-9-vinylcarbazole (sulfur content, 7.18%) 80methyl-S-chloroindole-n-odtyl perchlorate g 0.01

The above ingredients were uniformly mixed to form a solution andapplied to a paper treated with polyvinylalcohol to form a coating of711. thick (when dried) and dried.

Photosensitive papers not containing any sensitizing dye were alsoprepared for comparison.

After seasoned, the photosensitive papers were charged with anelectrostatic paper analyzer (supplied by Kawaguchi Denki) and exposedto a tungsten lamp and the exposure amount requiring decreasing thepotential to /2 of the value of the initial potential was measured.Ratios of reciprocals of the exposure amount are listed in Table 4 belowwhere the reciprocals for C, D and E of nonsensitized photosensitivepaper are used as unit.

within the scope of the present invention while C to E are controls.

TABLE 4 N on-sensitized Sensitized photophoto- Organic photoconsensitivesensitive ductive material paper paper EXAMPLE 7 Poly-9-vinylcarbazole(Luvican M-170) (1 g.) was dissolved in 15 ml. of monochlorobenzene, and0.5 g. of chlorinated parafiin (Empara-40, trade name) was addedthereto. In the resulting solution, 2 mg. of dye as shown below per 1ml. of dimethylsulfoxide was dissolved and coated on a high grade paperhaving a polyvinylalcohol coating by using a wire-round rod to form afilm layer of 5p. thick (when dried) and then dried.

The resulting photosensitive paper was allowed to stand in a constantmoistening box of RH. 60% for two days, and then charged with anelectrostatic paper analyzer (supplied by Kawaguchi Denki) and exposed.The exposure amount necessary for decreasing the initial potential to /2of the original value was measured. The result is shown in Table 5below.

The dyes used in this example have the following formula:

We claim:

1. An electrophotographic photosensitive material which comprises anorganic photoconductive material selected from the group consisting ofpoly-9-vinylcarbazole and derivatives thereof and at least one ofdialkylaminostyryl dyes having the formula:

wherein R is hydrogen loweralkyl or loweralkenyl and R is, similar ordissimilar, selected from the group consisting of hydrogen andloweralkyl or loweralkenyl; R and R are, similar or dissimilar, selectedfrom the group consisting of hydrogen and substituents having Hammettssubstituent constant a not lower than 0.2, but R and R should not besimultaneously hydrogen; R is an alkyl having 6 to 12 carbon atoms; R,and R are, 81mllar or dissimilar, loweralkyl; X is an anion; and n is 1or 2.

2. An electrophotographic photosensitive material according to claim 1in which the poly-9-vinylcarbazole derivative is selected from the groupconsisting of chlorinated poly-9-vinylcarbazole (chlorine content, 243%by weight), brominated poly-9 vinylcarbazole (bromine content, 17-46% byweight), chlorinated and brominated poly-9-vinylcarbazole, chlorinatedand iodinated poly-9- vinylcarbazole, cyanogenatedpo1y-9-vinylcarbazole, thiocyanated poly-9-vinylcarbazole,poly-3-methyl-9-vinylcarbazole, and chlorinatedpoly-3-methyl-9-vinylcarbazole.

3. An electrophotographic photosensitive material according to claim 1wherein R is a member selected from the group consisting of n-hexyl,sec-hexyl, n-heptyl, n-

V octyl, n-dodecyl, n-nonyl and 2-ethylhexyl.

4. An electrophotographic photosensitive material according to claim 1wherein R is nitro and R is hydrogen.

5. An electrophotographic photosensitive material according to claim 1wherein R and R are halogens, respectively.

6. An electrophotographic photosensitive material according to claim 1,wherein R is nitro and R is a halogen.

7. An electrophotographic photosensitive material according to claim 1wherein R is a halogen and R is hydrogen.

References Cited UNITED STATES PATENTS 3,575,698 4/1971 Mm'akami et al.961.6

3,666,464 5/1972 Keller et a1. 252-501 X 3,627,524 12/1971 Kinjo et a1.961.6 X

FOREIGN PATENTS 964,875 7/1964 Great Britain 96-1.6

OTHER REFERENCES Namba et al., Color Sensitization of Zinc Oxide WithCyanine Dyes, Journal of Phys. Chem, March 1965, pp. 774-779.

ROLAND EB. MARTIN, 1a., Primary Examiner US. Cl. X.R. 2'60-240 D, 240.9

